Dietary factors in circadian rhythm modulation and their impact on metabolic diseases: a state of the science review

Biological functions of living things are regulated by the circadian rhythm, a 24-hour cycle. Master clock in the hypothalamus is dependent on light-dark signals, while peripheral clock (present in organs) is cell-independent being synchronized with central clock. Mammals' circadian clocks control various catabolic and anabolic processes in their peripheral tissues. Peripheral organs display tissue-specific differences in the circadian period and phase and exhibit a circadian oscillator. Various diets will affect the peripheral clock in different organ systems. Ketogenic and high-fat diets can alter clock gene expression, while intermittent fasting shows improved circadian rhythm desynchronization. High-sugar diets can cause circadian rhythm-dependent gene amplification involved in hepatic carbohydrate and fat metabolism, leading to dyslipidemia and disturbed metabolism. High-salt diets can increase peripheral clock gene expression. Different diets can affect the peripheral clock rhythm, causing phase shifts, leading to the desynchronization of the central and peripheral clocks subsequently leading to various metabolic diseases.